the radiation report.
Apr. 23rd, 2010 02:11 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
solipsistnationSo, I had my radioactive watches measured yesterday by UCSC's Radiation Control Officer (who just started here after working for the state of Florida for a while and had some great stories to tell).
Of the 4 watches I've been wearing, the hottest was the broken one, measured at 0.5mR/h at the front, and a negligible dose from the back (that is, straight into my wrist).
Figuring I wear them for 12 hours a day, that would be 6mR per day of wearing a radium watch at most. Not GREAT, but not bad and mostly aimed away from me. It is, in fact, the same dose you get per hour from cosmic rays on a high-altitude flight. Figuring wearing a hot watch for 300 days out of the year, that's 1800mRem/year. That's about 6 times the normal average dose for just being in the world (according to this calculator). From that page: "International Standards allow exposure to as much as 5,000 mrems a year for those who work with and around radioactive material." So, as much as a radioactive material worker.
The problem with watches being radioactive, though, is working on them. To work on a watch, you have to get right up close and stick your face within a couple of inches. Radiation effects over most of your body are based on probability-- for X exposure, you have an extra Y percent chance of developing cancer (or whatever). For this amount, it's pretty small. Your eyes are another matter, though. Turns out there's something called "radiation cataracts", which are based on the total exposure of the lens of your eye to radiation. Enough radiation, and you just kinda develop cataracts. The good thing is that plexiglas or even eyeglass lenses (and, presumably the lenses in a watchmaker's loupe) blocks most of the radiation. Still, get up close and squint at a radium dial and you're zapping your lens a little more toward cataracts.
The other bonus is that radium paint dries up and flakes off. Thus, you have little bits of radium floating around in your junk watch box, decaying into nasty things like radon gas (not a big deal, probably, since it's around anyway) which fairly quickly decays into short-lived but nasty things which decay into lead-210, which has a half-life of 22 or so years. They hang around getting on other stuff and being generally unpleasant and filling your junk watch box with little tiny radioactive particles. Fun times all around. In small amounts in a room? Not really a big deal. Sealed inside a watch case? Not a big deal unless you open the case. It's worth noting, however, the that RSO asked me not to open the bag containing a loose watch movement and dial (which were clearly from before the radium watch paint standards and limits were defined in the 50's or so) to avoid getting any particles on his hands or contaminating his instruments, which could cause problems using them later.
On the other hand, he told me what I hoped, which is that my nice watches are safe to wear, but not to get my eyeballs up too close without a lens between the watch and me and to keep them in a box or something when I'm not wearing them. A wooden box is fine, just as long as it's thick enough to block stray particles.
Anyway, that's the deal with my radioactive watches.
Of the 4 watches I've been wearing, the hottest was the broken one, measured at 0.5mR/h at the front, and a negligible dose from the back (that is, straight into my wrist).
Figuring I wear them for 12 hours a day, that would be 6mR per day of wearing a radium watch at most. Not GREAT, but not bad and mostly aimed away from me. It is, in fact, the same dose you get per hour from cosmic rays on a high-altitude flight. Figuring wearing a hot watch for 300 days out of the year, that's 1800mRem/year. That's about 6 times the normal average dose for just being in the world (according to this calculator). From that page: "International Standards allow exposure to as much as 5,000 mrems a year for those who work with and around radioactive material." So, as much as a radioactive material worker.
The problem with watches being radioactive, though, is working on them. To work on a watch, you have to get right up close and stick your face within a couple of inches. Radiation effects over most of your body are based on probability-- for X exposure, you have an extra Y percent chance of developing cancer (or whatever). For this amount, it's pretty small. Your eyes are another matter, though. Turns out there's something called "radiation cataracts", which are based on the total exposure of the lens of your eye to radiation. Enough radiation, and you just kinda develop cataracts. The good thing is that plexiglas or even eyeglass lenses (and, presumably the lenses in a watchmaker's loupe) blocks most of the radiation. Still, get up close and squint at a radium dial and you're zapping your lens a little more toward cataracts.
The other bonus is that radium paint dries up and flakes off. Thus, you have little bits of radium floating around in your junk watch box, decaying into nasty things like radon gas (not a big deal, probably, since it's around anyway) which fairly quickly decays into short-lived but nasty things which decay into lead-210, which has a half-life of 22 or so years. They hang around getting on other stuff and being generally unpleasant and filling your junk watch box with little tiny radioactive particles. Fun times all around. In small amounts in a room? Not really a big deal. Sealed inside a watch case? Not a big deal unless you open the case. It's worth noting, however, the that RSO asked me not to open the bag containing a loose watch movement and dial (which were clearly from before the radium watch paint standards and limits were defined in the 50's or so) to avoid getting any particles on his hands or contaminating his instruments, which could cause problems using them later.
On the other hand, he told me what I hoped, which is that my nice watches are safe to wear, but not to get my eyeballs up too close without a lens between the watch and me and to keep them in a box or something when I'm not wearing them. A wooden box is fine, just as long as it's thick enough to block stray particles.
Anyway, that's the deal with my radioactive watches.